The specific objectives of the Neurohistology Core are to provide neuroanatomic and neuropathologic support for several aspects of the research comprising the Program Project and other activities of the laboratory. This arrangement has worked very well during the past 5 years. This includes the morphologic analysis of some of the mouse and rat brains arising from 1) the neuroanatomy projects, 2) Neurobehavior Research Project , 3) and 4) Neurophysiology Research Project. Some of the additional activities of the laboratory include the processing of human brains of individuals with learning disorders and control specimens, which are used to describe neuroanatomic findings and generate neuroanatomic hypotheses that can be tested in animal models such as those in the present Program Project. The Neurohistology Core will be responsible for insuring proper collection, registration, randomization, and processing of all neuroanatomic materials generated by the component projects. This core will determine the presence, location, and severity of cortical malformations in mice from the neuroanatomic, behavioral, and neurogenetic experiments. The Neurohistology Core will play the most involved role in the Neurogenetics Component. All offspring generated by this component will be screened by the core for both macro- and microscopic structural abnormalities. Our primary interest is in nervous system abnormalities, however, the entire animal will be grossly examined to look for any obvious defects in external structure (e.g. polydactyly) and in internal organs (e.g. situs inversus) that may correlate with brain changes. Additional markers of brain involvement, e.g., hippocampal anomalies, will be screened as well. Additional neuroanatomic studies, which include surgery or other specialized manipulations, morphometric studies, special processing such as immunofluorescence, autoradiography, tracer methods, immunohistochemistry, in situ hybridization will be carried out within the specific neuroanatomic projects themselves. The Neurohistology Core will maintain all the neuroanatomic materials, processed and unprocessed.